
Kate B. answered 04/19/21
MCAT Tutor Specializing in Bio/Biochem and Psych/Soc
Let me know if this helps!
First question:
- say that XR indicates normal vision (dominant) and Xr indicates colorblind vision (recessive). The mother is XRXr because she is a heterozygous carrier
- The father, a normal male, is XRY
- Therefore the Punnet Square is XRXr (mother) crossed with XRY (father)
- See if you are able to figure out the rest of the problem with this information!
Second Question:
- The mother is a female with colorblindness. Because colorblindness is recessive, her genotype must be XrXr
- It does not matter what the fathers genotype is, because any male progeny will have an XY genotype where the Y allele is from the father and the X allele is from the mother. Because the X allele in the male will always be from the mother, all sons will have a genotype of XrY, meaning that all sons will have a colorblind phenotype
I tried to upload a photo of a Punnet square, but was unable to. Please contact me if you need more help with a Punnet square drawing!
Isaaih S.
I appreciate it .04/19/21